Worlds can collide in tennis, too. In Thursday night's U.S. Open quarterfinal match, Roger Federer runs head on into Gael Monfils.
Federer, at 33, continues to maximize the enormous tactical and physical skills that have won him a record 17 major tournaments and five Opens. Monfils, the 28-year-old Frenchman admired by colleagues for his exceptional athleticism, also brings the kind of histrionics that don't necessarily tip the scales in his favor.
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While Federer plays with an emotional evenness, Monfils admits to lapses of commitment and fusses with himself and umpires, juxtaposing eccentric behavior with delightful shot-making.
Monfils -- 2-7 vs. Federer in his career, and 0-3 in majors -- never has been past a Grand Slam quarterfinal, and acknowledged he is the rare pro who has been without a coach for 18 months because, in part, "I don't think I'm easy. But I think I'm quite a good worker.''
Of the 24th-ranked Monfils, Federer said, "He's got, easily, top 10 potential. He's a great mover. He's got a wonderful serve, really, which nobody really talks about because his athletic movement stands out so much.''
Federer pointed to Monfils' occasional struggle with injuries in holding him back. Federer also said, "Sometimes, not wanting to play because of reasons only he can explain. But I think I can speak on behalf of so many players: We love watching him play.''
For the first time, Monfils has reached a second Slam quarterfinal in the same year; he lost to Andy Murray in the French Open. This equals his deepest run in the U.S. Open; he lost to Novak Djokovic in the 2010 quarters at Flushing Meadows.
"He can hit shots other players can't,'' Federer said, "so you have the danger in the back of your mind. And a big, powerful serve that keeps him out of trouble.''
Now, though, Monfils appears to be catching Federer at Federer's reinvigorated best. Fully recovered from back discomfort last year, Federer has embellished his already keenly balanced game by attacking the net 160 times in his first four matches, more often than any other quarterfinalist.
But Monfils, who called Federer the "legend of tennis . . . the greatest tennis player we've ever had,'' evaluated Thursday night's duel with a characteristic nonchalance.
"Against Federer? Why not?'' he said. "I played Rafa [Nadal] one time here and it was pretty much even. So, why not?''